Technical Abstract:
South Texas has experienced increases of several invasive grasses including tanglehead (Heteropogon contortus [L.] P. Beauv. ex Roem & Schult.). There is relatively little research concerning the effects of tanglehead on ecosystem processes such as energy cycling, nutrient cycling, and microbial soil processes in this region. To examine the effects of tanglehead invasion on microbial soil processes we are currently evaluating microbial community size and structure in 3 different types of vegetation communities in the Texas Coastal Sandsheet, representing a tanglehead invasion gradient including: (1) native plant community, (2) tanglehead-native mixture, and (3) tanglehead dominant. Soil microbial communities were evaluated for microbial biomass C (MBC) and N (MBN) as well as community structure via FAME profiles. Soil MBC was greater in native plant communities than both tanglehead mixture and dominated communities. Soil MBN was also greater in native plant communities than both tanglehead mixture and dominated communities. Mean microbial composition and fungi:bacteria ratio differed between tanglehead dominated and native vegetation communities. Nonmetric multidimensional scaling ordination reveals shifts in the microbial community composition related to changes in bacteria and fungal abundance. The changes in microbial community size and structure suggest potential changes in soil quality and microbial functioning due to tanglehead invasion. Further research will help to determine the extent of these effects on wildlife habitat, and how to more efficiently focus habitat management and restoration efforts in south Texas.